Radio frequency amplifier

Abstract

A radio frequency amplifier includes: a transistor; an input line; an output line; and a shunt circuit that is connected between ground and the input line or the output line, wherein the shunt circuit includes: a first series resonant circuit that includes an inductor and a capacitor that are connected in series and has first resonant frequency f1; a second series resonant circuit that includes an inductor and a capacitor that are connected in series and has second resonant frequency f2 that is different from the first resonant frequency; and a resistor that is connected between a first connection point and a second connection point, the first connection point being a connection location between the inductor and the capacitor in the first series resonant circuit, the second connection point being a connection location between the inductor and the capacitor in the second series resonant circuit.

1 . A radio frequency amplifier comprising:
 a transistor;   an input line that transmits a radio frequency (RF) signal to be inputted into the transistor;   an output line that transmits an RF signal that is outputted from the transistor; and   a shunt circuit that is connected between ground and the input line or the output line, wherein   the shunt circuit includes:
 a first series resonant circuit that is connected between a node and the ground, includes a first inductor element and a first capacitor element that are connected in series, and has a first resonant frequency, the node being on the input line or the output line; 
 a second series resonant circuit that is connected between the node and the ground, includes a second inductor element and a second capacitor element that are connected in series, and has a second resonant frequency that is different from the first resonant frequency; and 
 a first impedance element that is connected between a first connection point and a second connection point and includes a resistance component, the first connection point being a connection location between the first inductor element and the first capacitor element, the second connection point being a connection location between the second inductor element and the second capacitor element. 
   
     
     
         2 . The radio frequency amplifier according to  claim 1 , wherein
 the transistor includes:
 a gate; 
 a drain; and 
 a source, and 
   the first inductor element and the first capacitor element are a transmission line and a bypass capacitor, respectively, that are included in a drain bias circuit that supplies a bias voltage to the drain, or are included in a gate bias circuit that supplies a bias voltage to the gate.   
     
     
         3 . The radio frequency amplifier according to  claim 2 , wherein
 the first connection point and the second connection point are connected by a series circuit, the series circuit including the first impedance element and a direct current (DC)-blocking element.   
     
     
         4 . The radio frequency amplifier according to  claim 1 , wherein
 the first impedance element is a resistor element.   
     
     
         5 . The radio frequency amplifier according to  claim 1 , wherein
 the shunt circuit further includes a third series resonant circuit that is connected between the node and the ground, includes a third inductor element and a third capacitor element that are connected in series, and has a third resonant frequency that is different from the first resonant frequency and the second resonant frequency.   
     
     
         6 . The radio frequency amplifier according to  claim 1 , wherein
 in the first series resonant circuit, the first inductor element is connected closer to the node than the first capacitor element is.   
     
     
         7 . The radio frequency amplifier according to  claim 1 , wherein
 the first impedance element is connected between a node and the ground and includes a direct current (DC)-blocking element, the node being a node at which the first connection point and the second connection point are shorted.   
     
     
         8 . The radio frequency amplifier according to  claim 1 , wherein
 an impedance element that blocks signals of the first resonant frequency and the second resonant frequency is absent between the shunt circuit and a gate or a drain of the transistor.   
     
     
         9 . The radio frequency amplifier according to  claim 8 , wherein
 an impedance of the impedance element is 20Ω or greater.   
     
     
         10 . The radio frequency amplifier according to  claim 1 , wherein
 the resistance component is 60Ω or less.   
     
     
         11 . The radio frequency amplifier according to  claim 1 , wherein
 the resistance component is 30Ω or greater.   
     
     
         12 . The radio frequency amplifier according to  claim 5 , wherein
 the first resonant frequency, the second resonant frequency, and the third resonant frequency are arranged at equal intervals on a logarithmic scale.